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Abstract

Background: Magnetocardiography (MCG) measures the magnetic field induced by the electrical current generated during the cardiac cycle. Since electric current is affected by ischemic damage, MCG can thereby be used to noninvasively detect and localize said damage due to acute coronary syndrome (ACS).

Hypotheses: We hypothesize that a novel 3D current density mapping method for visualizing MCG is efficacious in detecting and localizing ischemic damage when compared to gold standard dismissal diagnosis as the primary measure.

Methods: MCG-derived current density maps were created for a cohort of 28 prospectively enrolled high risk unstable angina (UA) patients diagnosed by ACC/AHA guidelines. The first 16 patients’ maps were used to calculate sensitivity and specificity in a single-blinded study. Unblinded normal (n = 11) and ischemic (n = 7) sub-cohorts were selected from the full cohort based on certain inclusion and exclusion criteria. The 17-segment AHA model was used to localize differences in electrical conductivity that may be an indicator of ischemic damage due to ACS in the diseased cohort compared to the normal. A 1-sample Student test was used to show differences in each segment between the two cohorts.

Results: Our proposed method was found to have a sensitivity of 57% and specificity of 33% compared to gold standard dismissal diagnosis. Figure 1 compares current density magnitudes in each segment between an exemplary ischemic case and the mean of the normal cases. The ischemic data indicates segments of abnormal repolarization that were significantly different when compared to normal counterparts (p < 0.001). The significant regions are localized in the left anterior descending artery segments of the 17-segment AHA model.

Conclusion: The proposed method is highly sensitive when compared to gold standard in diagnosing ACS in high risk UA patients, reinforcing the role of MCG in early non-invasive detection and localization of ischemic damage due to ACS.